96,234 research outputs found

    Single spin detection by qubit SWAP to a molecular nanomagnet

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    Spin state detection is a key but very challenging step for any spin-based solid-state quantum computing technology. In fullerene based quantum computer technologies, we here propose to detect the single spin inside a fullerene by transferring the quantum information from the endohedral spin to the ground states of a molecular nanomagnet Fe8_{8}, with large spin S=10. We show how to perform the required SWAP operation and how to read out the information through state-of-the-art techniques such as micro-SQUID.Comment: Europhysics Letters 69,699 (2005

    Efficient Contact State Graph Generation for Assembly Applications

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    An important aspect in the design of many automated assembly strategies is the ability to automatically generate the set of contact states that may occur during an assembly task. In this paper, we present an efficient means of constructing the set of all geometrically feasible contact states that may occur within a bounded set of misalignments (bounds determined by robot inaccuracy). This set is stored as a graph, referred to as an Assembly Contact State Graph (ACSG), which indicates neighbor relationships between feasible states. An ACSG is constructed without user intervention in two stages. In the first stage, all hypothetical primitive principle contacts (PPCs; all contact states allowing 5 degrees of freedom) are evaluated for geometric feasibility with respect to part-imposed and robot-imposed restrictions on relative positioning (evaluated using optimization). In the second stage, the feasibility of each of the various combinations of PPCs is efficiently evaluated, first using topological existence and uniqueness criteria, then using part-imposed and robot-imposed geometric criteria

    Robust Procedures for Obtaining Assembly Contact State Extremal Configurations

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    Two important components in the selection of an admittance that facilitates force-guided assembly are the identification of: 1) the set of feasible contact states, and 2) the set of configurations that span each contact state, i.e., the extremal configurations. We present a procedure to automatically generate both sets from CAD models of the assembly parts. In the procedure, all possible combinations of principle contacts are considered when generating hypothesized contact states. The feasibility of each is then evaluated in a genetic algorithm based optimization procedure. The maximum and minimum value of each of the 6 configuration variables spanning each contact state are obtained by again using genetic algorithms. Together, the genetic algorithm approach, the hierarchical data structure containing the states, the relationships among the states, and the extremals within each state are used to provide a reliable means of identifying all feasible contact states and their associated extremal configurations

    Doping and energy evolution of spin dynamics in the electron-doped cuprate superconductor Pr0.88_{0.88}LaCe0.12_{0.12}CuO4δ_{4-\delta}

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    The doping and energy evolution of the magnetic excitations of the electron-doped cuprate superconductor Pr0.88_{0.88}LaCe0.12_{0.12}CuO4δ_{4-\delta} in the superconducting state is studied based on the kinetic energy driven superconducting mechanism. It is shown that there is a broad commensurate scattering peak at low energy, then the resonance energy is located among this low energy commensurate scattering range. This low energy commensurate scattering disperses outward into a continuous ring-like incommensurate scattering at high energy. The theory also predicts a dome shaped doping dependent resonance energy.Comment: 8 pages, 4 figures, added discussions, replotted figures, and updated references, accepted for publication in Phys. Rev.